This core will create site-directed mutations of the alpha and beta globin subunits of human hemoglobin and will over-express these modified globins in E. coli using protocols that were optimized during last funding period of this Program Project Grant. In addition, strategies will be devised for producing globin subunits in which only a single type of amino acid is labeled with 13C. The frozen E. coli cell pasted produced in this core will be shipped to the Hemoglobin Assembly Core where the mutant hemoglobin tetramers will be assembled and purified.